Change mbedtls_ssl_tls13_key_schedule_stage_handshake() to use psa_raw_key_agreement()

Signed-off-by: Przemyslaw Stekiel <przemyslaw.stekiel@mobica.com>

library/ssl_tls13_keys.c

diff --git a/library/ssl_tls13_keys.c b/library/ssl_tls13_keys.c
index 5615386..540c6e0 100644
--- a/library/ssl_tls13_keys.c
+++ b/library/ssl_tls13_keys.c
@@ -1116,6 +1116,7 @@
 int mbedtls_ssl_tls13_key_schedule_stage_handshake( mbedtls_ssl_context *ssl )
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    psa_status_t status = PSA_ERROR_GENERIC_ERROR;
     mbedtls_ssl_handshake_params *handshake = ssl->handshake;
     mbedtls_md_type_t const md_type = handshake->ciphersuite_info->mac;
     size_t ephemeral_len = 0;
@@ -1136,15 +1137,29 @@
         if( mbedtls_ssl_tls13_named_group_is_ecdhe( handshake->offered_group_id ) )
         {
 #if defined(MBEDTLS_ECDH_C)
-            ret = mbedtls_ecdh_calc_secret( &handshake->ecdh_ctx,
-                                            &ephemeral_len, ecdhe, sizeof( ecdhe ),
-                                            ssl->conf->f_rng,
-                                            ssl->conf->p_rng );
-            if( ret != 0 )
-            {
-                MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ecdh_calc_secret", ret );
-                return( ret );
-            }
+        /* Compute ECDH shared secret. */
+        status = psa_raw_key_agreement(
+                    PSA_ALG_ECDH, handshake->ecdh_psa_privkey,
+                    handshake->ecdh_psa_peerkey, handshake->ecdh_psa_peerkey_len,
+                    handshake->premaster, sizeof( handshake->premaster ),
+                    &handshake->pmslen );
+        if( status != PSA_SUCCESS )
+        {
+            ret = psa_ssl_status_to_mbedtls( status );
+            MBEDTLS_SSL_DEBUG_RET( 1, "psa_raw_key_agreement", ret );
+            return( ret );
+
+        }
+
+        status = psa_destroy_key( handshake->ecdh_psa_privkey );
+        if( status != PSA_SUCCESS )
+        {
+            ret = psa_ssl_status_to_mbedtls( status );
+            MBEDTLS_SSL_DEBUG_RET( 1, "psa_destroy_key", ret );
+            return( ret );
+
+        }
+        handshake->ecdh_psa_privkey = MBEDTLS_SVC_KEY_ID_INIT;
 #endif /* MBEDTLS_ECDH_C */
         }
         else if( mbedtls_ssl_tls13_named_group_is_dhe( handshake->offered_group_id ) )